There are many existing absolute value encoder transmission protocols, such as an EnDat protocol, a BISS protocol and an RS485 protocol (hereafter also referred to as “485” or “485 protocol”), and most of these protocols follow RS485 and RS422 protocols on hardware. Their transmission rates are limited to their transmission distances, and difficultly achieve the existing speed (2.5 Mbps) when the transmission distance is far. For a multi-axis robot (a robot having 6-9 axes), the above communication manner needs 6-9 4-core cables independent each other for transmission, which is not beneficial to stability of the system, and the price of the cable is relatively expensive. An encoder data transmission manner based on an MAC protocol or other protocols has high delay, and is not adapted to many robot systems having high real-time requirement. In addition, when closed loop control is made in the robot system, encoder position feedback of many bus communication needs three or more periods, which is not beneficial to higher-precision movement control.